·
As
feed passes through the earthworm gut the material is mineralized and plant
nutrients are available.The grinding
effect of the gizzard and the passage through the gut leads to the formation of
a granule (15) (16).

·Casts
have a structure that is similar to a slow release granule: it has an organic
matter core and a clay casing (1).

·NH4
levels are high in fresh casts but casts stabilize after 2 weeks of aging
through nitrification.The acidity level
in casts is slightly low, which reduces denitrification (5).
Salinity levels are moderate in casts, since passage through the earthworm gut
does not increase the level of some salts (Ca, Mg, Na)
(2).

·
Some
composts have high concentrations of ammonium or
soluble salts (6).There are
larger amounts of NH4 than NO3 in composted domestic
waste.High Levels of NH4 are
due to non-stabilized substances (4).Immature (unfinished) compost can stunt or
kill plants, and reduce germination and growth (11).

Comparison as to pathogens

·Recycling organic waste through earthworms
also results in a product with a lower pathogen level than compost (8).

·
Since
high temperature are not part of the earthworm cast production process disease
suppressing microorganisms that may be present in this material survives in the
absence of heat (20).

·Some composts are
suppressive of plant pathogens but heating them to 60oC for five
days reduced suppressiveness. This is why some composts need to be inoculated with disease suppressing
microorganisms. Adding nutrients (i.e.
reducing competition) also reduces disease suppression by composts (21).

Comparing
Earthworm Casts and Compost as to their processes

Comparison as to time and volume requirement

·
Earthworms
eat 75% of their weight daily (Ndegwa, 1999) and the
speed or earthworm casts production can be increased by increasing the amount
of earthworms.The layer of waste needs
to be 1 ft or thinner to prevent anaerobic conditions which hinder earthworm
activity.

·
A
compost pile needs to be 3 cubed feet to hold heat in winter and takes 3-4
months to be cured (22).

Comparison as to odor problem

·
Odorous
gases are emitted as compost piles heat up. Specific layering of composting
material needs to be used to prevent odor.

·
Earthworms
don’t require heat to process waste (heat is actually detrimental).In the correct waste to worms ratio
fermentation and heat can be prevented, and also odor or flies.

(1) Casts have a
structure that is similar to a slow release granule: it has an organic matter
core and a clay casing.

Casts Structure

In Chan
& Heenan (1995) worm casts had a composite
structure, made of units 210-500 micro-m in diameter which were made of
smaller spherical subunits (50-100 micro-m).Casts were significantly more water stable and higher in total
nitrogen than in soil aggregates of the same size.Porosity in the casts was created by spaces
between the subunits, which were composed of very densely packed clay/silt
size particles.Evidence from scanning
electron microscopy suggests the high stability to be due to the presence of
cements (Chan & Heenan, 1995).In Fragosoet al. (1993) casts structure of the Trigaster earthworm species showed granules composed of
organic debris fractions (250-2000 mm).When earthworms were added to soil made of 1-2 mm aggregates (Schrader
et al. 1994), molding processes in
the earthworm gut destabilized the soil structure but at the same time
biochemical processes act as an antagonistic stabilizing system.Shipitalo (1986)
observed that freshly deposited moist casts were 26 to 41% more dispersible
than uningested moist soil due to disruption of
some existing bonds during gut transit.When casts were aged or dried there was a stronger bond of plant
microbial polysaccharides and other organic materials to clay, predominantly
via clay-polyvalent catio-organic matter (C-P-OM)
linkages involving calcium (Shipitalo, 1986).Zhang & Schrader (1993) showed that
organic C and CaCO3 act as bonding agents and the CaCO3
is involved with binding linkages with organic matter during digestion, the
more stable are the formed aggregates.They also observed that in L. terrestris
casts were very water stable, maybe due to the
presence of Ca humate or organic matter-polyvalent cation-soil particle bonds.Organic C in those same casts increased by
21 to 43%.Water extractable
polysaccharides increased too, maybe due to enrichment of mucopolysaccharides
during ingestion, or from cutaneous polysaccharides
(Zhang & Schrader, 1993).In Marinissen & Dexter (1990) aging made casts more
stable, probably due to fungi that developed on the surface of 6 days old
casts.Artificial casts were made by
molding soil at 100% moisture and pushing it through a 1.5 mm opening syringe,
and compared to natural casts as to stability, which was measured as the
capacity to prevent clay dispersion.Internal stability was measure by breaking down casts (magnetic
stirrer) and the external one by using a paddle stirrer. Stability of the
aggregate surface increased with aging but was the internal stability
remained the same.Since internal
stability seems to depend on % of microaggregates,
no new ones were formed (Marinissen & Dexter,
1990). Shipitalo & Protz
(1989) observed that earthworms fragmented litter by grazing and a liquefied
soil and debris mixture formed in their gut.In the gizzard, more fragmentation, microbial activity and digestive
enzymes decompose organic matter, which becomes part of the soil plasma.Lignified particles resist fragmentation
and clay minerals are brought close to newly formed bonding agents
(polysaccharides).The organic matter
enriched plasma adheres to surfaces of the organic skeleton of resistant
organic fragments (with the help of bonding material), forming new
aggregates.Pellets are excreted in
this state and both drying and aging strengthens the bond between organic and
mineral components.Therefore Shipitalo & Protz (1989)
concluded that ingestion of soil and litter in earthworms brings clay in
close contact with decomposing organic fragments, creating the organic matter
cored microaggregates.Organic matter is therefore encapsulated by
clay and it resists rapid decomposition.The linkages within the aggregates consist of clay-polyvalent cation - organic matter (C-P-OM) bonds and they seem to
make aggregates more stable.

(2) Salinity levels
are moderate in casts, since passage through the earthworm gut does not
increase the level of some salts (Ca, Mg, Na).

Salinity in Earthworm Casts

Casts seems to reduce the
salinity problem caused by an excess of NH4 in an experiment where
tomato plants were grown in sand, clayey loam, and garden soil processed by
Californian earthworms. Feeding with NH4 (instead of NO3) slowed
down plant growth in sand, less in loam, and not at all in soil processed by
earthworms (Borowski, 1995).Baskeret al. (1993) observed that
exchangeable Ca, Mg and Na were marginally higher in casts than in
non-ingested soil, soil, and that ingestion by earthworms increased he potassium level of the soil.

In the 1980’s, at a research station in Rothamsted, earthworms were collected and put in buckets
of clean water, in batches of 250.A
solution of 0.2% formaldehyde was spread on the field to drive the worms out
of their burrows.They were then
rinsed in a second bucket of clean water and spread at a rate of 250 worms m-2 over a landfill site capped with 15cm
of clay subsoil, treated with domestic dried sewage solid at 10 tons ha-1
and planted with grass.A higher plant
growth was observed in the presence of worms (Edwards & Bates,
1992).According to Haimi (1992) birch seedlings planted in soil with earthworms
had 33% and 24% more leaf and stem biomass respectively than in those grown
in pots without earthworms.Root
biomass was slightly lower in the earthworms than in the bare soil treatment
and N content of leaves was twice higher in the treatment with earthworms.This was only partially explained by
earthworm mortality.N uptake
increases in the presence of earthworms and is correlated (r = 0.85) with the
increase in CO2 production (Ruz – Jerez, 1992).

(3) Plants treated
with compost may still show N deficiency, even when synthetic fertilizer is
added.His is due to N immobilization:
microorganisms in compost use N for their metabolism.

Nutrient Dynamics in Compost

Cocomposted sewage sludge is obtained by
aerobic digestion of municipal refuse and anaerobically
digested sewage sludge.N
immobilization can be a problem in these composts. Plants showed N deficiency
symptoms even when supplied with NH4NO3, along with
reduced dry matter production and lower plant N concentrations.Also there was no difference between the
11, 22 and 44 tons of compost ha-1.Therefore when applied at agronomic rates
compost can support plant growth, id adequate amounts of supplemental N
fertilizers are used (Sims, 1990).

(4) There are larger
amounts of NH4 than NO3 in composted domestic
waste.High Levels of NH4
are due to non-stabilized substances.

Nutrient Dynamics in Compost

Composted urban refuses were studied as organic
fertilizers (Villar et al., 1993).Most of the total N was in organic forms;
NH4 was more abundant than NO3, and calcium was the
most abundant nutrient followed by K, Na, Mg and P.Most of the Ca and Na were in available
forms; available K and Mg were lower and available P very small.Although compost was unbalanced with regard
to the main nutrients, it had potential agronomic value.Total C contents and C/N ratios in the
three non-amended composts were in the range for stabilized composts;
however, the NH4 content seemed to point to the presence of
non-stabilized substances (Villar et al., 1993).

(5) NH4
levels are high in fresh casts but casts stabilize after 2 weeks of aging
through nitrification.The acidity
level in casts is slightly low, which reduces denitrification.

Nutrient Dynamics in Earthworm
Casts

In fresh casts, NH4 levels were
very high (294.2-233.98 mg g-1 dry cast) due mineralization in
the earthworm gut.During the first
week of cast aging, NH4 levels decreased while NH3
levels increased, due to rapid nitrification in the fresh casts.After two weeks the levels of NH4
and NO3 were stabilized, probably due to organic matter protection
in dry casts (Decaens, 1999).Casts tend to stabilize through nitrification
after being deposited; in a garden soil processed by earthworm ammonium
underwent complete nitrification compared with 33 and 9% nitrification in
loam and sand, respectively (Borowski, 1995).In Decaens
(1999) C increased during cast aging
(+100%), possibly because of CO2 fixation or macrofaunal
activities in casts.Stabilized
earthworm casts leached less dissolvable organic carbon than from undigested
soil.Nutrient losses from casts that
underwent several wetting / drying cycles show that there was a strong
protection of nutrients in casts at first, but this was reduced as the
aggregate structure was weakened (McInerney et al.,
2000).After a 20 days long incubation
of fresh casts a rapid increase in mineral N was observed during the first
few days after deposition, and then a decrease to a level 4.5 times higher
than in the soil.Also the NH4
level was higher in fresh casts than in the control (Rangel, 1999). The
decrease of mineral N in time in casts can be due to N becoming microbial
biomass, volatilized, denitrified, or leached (Lavelle,
1992).In Haynes (1999) uningested soil and casts were incubated for 42 days, and
extractable P levels were similar in casts and soils during the initial
stages of incubation, but were larger in casts after 28 and 42 days.Activities of arylsulphatase
and acid phosphatase were lower in casts than in uningestedsoil, therefore the
mineralization of organic matter during gut transit could be the reason for
the increase in extractable P and S during incubation.Haynes (1999) concluded that mineral N
increases because of mineralization in the gut, but P and S levels increase
due to mineralization after egestion.In Lavelle (1992)
mineral N in casts was mostly in the form of ammonium, and after a 26 days
long incubation NH4 was nitrified or immobilized in biomass.The incubation of soil before ingestion
increased NH4 production in casts and being slightly acidic casts
do not favor the denitrification of NO3.Biomass N was stable (relatively) after an
initial flush on day 1.Processing by
earthworms increases lignin mineralization, as compared with just mixing with
soil and the passage in the gut might affect lignin structure (Scheu, 1993).

(6) Some composts have high concentrations of ammonium or soluble
salts.

Salinityin Compost

The salinity problem is
shown in O'Brien & Barker (1996) by the inhibitions in seed germination
and in plant growth in some composts, which is
associated with high concentrations of ammonium or soluble salts in the
media.Ammonium-N in the compost
declined with time (over 28 days), whereas nitrate-N and electrical
conductivity initially increased then decreased with time. Ammonium salts
appear to be lost from the compost more rapidly than nitrate salts, which
have a prolonged inhibitory effect on germination and growth (O'Brien &
Barker, 1996).

(18) Compost can be an incomplete fertilizer, most
plants have a an increase in yield with the addition
of compost, organic N sources can cause a short term yield decrease.

Effect of Compost on Plant Growth

An
increase in soil productivity, which cannot be explained by mineral nutrients
alone, is often recorded when composted organic wastes are supplied to
croplands.This is the so-called
"organic matter effect" suggests that mechanisms other than simple
nutrient supply can contribute to plant growth (Galli
et al. 1992).Hountin
et al. (1995) studied the effect of peat moss-shrimp wastes compost on barley
(Hordeumvulgare L.)
applied alone or with NPK, and he concluded that the main effect of compost
on straw yield, numbers of tillers, plant height, and number of ears was more
important than that of fertilizer.Compost
was considered incomplete as a fertilizer in Hartz
et al. (1996) when composted green yard and landscape waste and peat were
evaluated as to plant nutrient supply.Both were mixed with perlite and added to
pots planted with tomatoes and marigolds at a volume ratio of 1:1.Fertigation
regimes of 0, 50, or 100 mg L-1 of 15N-13P-12K).Compost was equivalent or superior to peat
in plant growth and it contributed to crop macronutrient nutrition, but the
highest fertigation rate was required for optimum
growth.In Chong
et al. (1991) deciduous ornamental shrubs were grown in 33%, 67%, and 100% of
three different sources of compost. Despite large variation in species growth
response to sources and levels of compost, most grew equally well or better
in the compost-amended regimes than in the control and were influenced
little, or not at all, by initial or prevailing salt levels in the media.
Shoot and root dry weight of some plants increased with increasing compost
levels. The reverse relationship occurred (all sources) in shoot and root dry
weight of privet and root dry weight of weigela and
potentilla. Leaf nutrients (N, P, K, Ca, Mg, Fe, Mn, and Zn) tended to increase with increasing compost
levels, but not all species showed this response with all nutrients.
Regardless of compost source or level, all shrubs were of marketable quality
when harvested, except privet, which showed leaf chlorosis
in all compost-amended regimes (Chong et al.,
1991).Fauci
& Dick (1994) observed that the efficiency of organic N uptake from
organic fertilizers varies with the type of fertilizer, and organic N sources
can cause short-term crop yield decreases.10-30% of N was taken up when poultry manure or pea vine residues were
added (Fauci & Dick, 1994).

(10) Bothare organic products which provide the
plant with nutrients, good soil aeration and other un-identified
advantages(the “organic matter
effect”)

(effect of compost on plant
growth)

An increase in soil
productivity, which cannot be explained by mineral nutrients alone, is often
recorded when composted organic wastes are supplied to croplands.This is the so-called "organic matter
effect" suggests that mechanisms other than simple nutrient supply can
contribute to plant growth (Galli et al. 1992).

(7) More decomposition
(Lignolysis) occurs and higher levels of Nitrogen
are reached when waste is fed to worms than in composting.Casts also increase protein synthesis in
plants.

Compost as Compared to Casts

In Vinceslas-Akpa
& Loquet (1997) lignocellulosic
wastes (of maple) were composted and vermicomposted (i.e. ingested by
earthworms) for 10 months under controlled conditions. At first, total
organic matter and carbon decreased rapidly, while cellulose was
decomposing.Aromatic structures and
lignin began to decompose after one month of composting.More ligninolysis
occurred in the vermicompost.The
C-to-N ratio decreased, showing changes in total C and higher levels of N in
the vermicompost.The two materials
evolved differently: casts had a lower aromaticity
ratio, and a higher protein-to-organic matter ratio than in compost, which
indicates a higher level of humification (Vinceslas-Akpa & Loquet,
1997).When casts and compost were
compared in a pot experiment casts increased protein synthesis in lettuce seedlings
by approximately 30%, whereas no differences were recorded in the presence of
compost (Galli et al. 1992)

(8) recycling organic waste through earthworms also results in a product with a lower pathogen
level than compost.

Compost as Compared to Casts (continued)

The process of vermicomposting can also result
in a product with a lower pathogen level than compost (Eastman, 1999).

(9) Slow nutrient
release is more synchronized with plant needs, and leads to higher yields.

Effect of Nutrient Availability and slow release on Plant Growth

When supplied with inorganic nitrogen, grain sorghum plants were
found to have a higher intake rate than when supplied with organic nitrogen (Jordan, 1996).Al-Karaki (1995)
exposed plants to P stress and found that lower dry matter in shoot and root
was due to less water uptake, and not to P deficiency.Catanazaro (1998)
showed the importance of the synchronization between nutrient release and
plant uptake by comparing alternate liquid fertilization, constant liquid fertilization,
resin coated slow release fertilizer and slow
release fertilizer tablets.When he provoked leaching less nutrients leached with the slow
release products.In the same
study slow release tablets caused nutrient deficiency and slow release resin
coated fertilizer had the most efficient N uptake 64-68% as compared to
41-46% in liquid fertilizer.Several
methods were tested by Choi & Nelson (1996) in
order to obtain a slow release fertilizer, which would be more synchronized
with the nutrient requirement of the fertilized plant: to prolong the period
of N a bacterium - Brevibacteriumlactofermentum - was bonded to kraft
lignin, a substance highly resistant to degradation. To retard mineralization
further, the bacterium-lignin mixture was reacted with formaldehyde to form
amino cross-links within and between protein chains. Bonding to lignin was
undesirable because N release occurred during the same period as from the
bacteria unbound to lignin and the total amount of N recovered was reduced to
only 42%. Cross-linking with formaldehyde was less desirable since N was
released mainly during the first 4 weeks and the total amount of N released
was even lower than for the bacterium-lignin mixture. Additions of urea to
the latter reaction did not improve subsequent N mineralization. In a second
set of treatments lignin was withheld and the bacterium was reacted with
formaldehyde. Five percent formaldehyde by weight (of the bacterium)
successfully reduced release of N during the first 4 weeks and increased it
thereafter. In this treatment N was released from week 2 through the end of
the test (12 weeks). Peak release occurred at 6 weeks. This resulting N
source could be combined with other slow-release N sources to form a slow
release N fertilizer (Choi & Nelson,
1996).Controlled release fertilizers were compared to water
soluble fertilizer as to nutrient leaching in Marigold plants (Cox,
1993).The controlled release
fertilizer was only more effective than soluble fertilizer at reducing
leaching when applied in 2 small doses instead of one (one at planting, the
other 15 to 35 days later).Leaching
is reducing by applying the controlled release fertilizer rather than
incorporating it in the medium.In all
fertilizer types and application methods NO3 was the predominant
type of N found in the leachate (Cox, 1993).

Effect of Casts on Plant Growth(continued)

The application of
earthworm casts (0, 100, and 300 g per 3.5 kg soil) increased the dry weight
of soybean by 40 to 70%. The nitrogen absorbed by the plants from the soil
increased to 30 to 50%.Phosphorous
and potassium in the plant were twice that of the control.The amount of organic matter, total
nitrogen, phosphorous and potassium in the soil also increased, as well as
available phosphorous and potassium in the soil (Lui
et al., 1991).The presence of
earthworm casts increase the uptake efficiency of nitrogen as shown in Zhao
et al. (1988) where the addition 15N labeled chemical fertilizer mixed with
earthworm casts increased the nitrogen utilization coefficient from 22.4 to
38.4% and that of the N-P fertilizer from 33.2 to 40.9%.In Hidalgo (1997) media: casts ratios of
1:1, 2:1 and 3:1 increased growth index, stem diameter, root growth, dry
weight, flower initiation and flower number compared to peat moss: perlite (7:3) and pine bark: sand (4:1).Earthworm casts were found to increase
nutrient uptake in Tomati (1994), including
nitrogen and several ions, particularly Mg and K.

Effect of Casts on Plant Growth(continued)

In Saciragic
et al. (1986) plants were given NPK or 2-10 kg casts m-2.Cabbages given 4 kg casts leeks given 10-kg
casts outyielded the NPK controls.Fodder sorghum given 10 kg of compost and
cut twice yielded only 60% as much dry matter as when given NPK (110-kg N m-2).It was concluded that fodder sorghum
required fertilizer as well as.Casts
are not only used in horticulture, but in agronomic crops too.

(14)Casts have a hormone like effect that increase germnination
and growth rate.

Effect of Casts on Plant Growth(continued)

Indole compounds were detected in the worms, but it was not
possible to identify specific auxins (Hidalgo, 1997).When
used in horticulture, earthworm casts have a hormone-like effect.The biological effect of casts is linked to
microbial metabolites that influence plant metabolism, growth and development
(Tomati et al., 1997).Casts of the earthworm Eisenia fetidaandrei increased
germination rate and enhanced seedling growth of cucumber seeds in Hidalgo (1999), and it was concluded that studies are needed
to determine if casts contain the plant-growth- promoting hormones and
available nutrients necessary to enhance germination and plant growth.

(15) As feed passes
through the earthworm gut the material is mineralized and plant nutrients are
available.

Production of Earthworm casts

As
explained by Edwards (1995), earthworms ingest organic matter and egest it as much finer particles after passing through a
grinding gizzard that they all possess. Worms feed on the microorganisms that grow upon the organic material.They take over the role of aerating
necessary in composting to maintain aerobic conditions and their turnover
rate is much higher than with composting as they process 3 feet deep layers
of suitable organic material in less than 30 days (Edwards, 1995).Edwards & Bates (1992) found Eisinafetida to be the best
choice due to its wide temperature and moisture tolerance, and because it is
a tough worm easy to handle and it out competes other species.Thee highest growth rate in Eisinafetida at 30oC
and 85% moisture.A maximum of cocoons
hatched at 20oC,
which was considered optimum growth temperature for this worm (Edwards &
Bates, 1992)

During
this process, N, P and Ca mineralized. Worms die at temperatures higher than
35oC, and they process OM best at temperature between 15 and 25oC, and a moisture of 70 to 90%.Different materials are mixed before processing for faster results and
a better product.Also worms have a
limited tolerance to some chemicals. The most commonly used earthworm is Eisinafetida and the best
results are obtained by using raised beds, feedstock is added at the top and
casts are collected at the bottom through mesh floors.In 25 kinds of vegetables, fruits or
ornamentals casts did better than compost or commercial potting mixes. (Edwards, 1995).There's scientific evidence that human pathogens do not survive the
vermicomposting process (Edwards and Bohlen, 1995).

(16)

As feed passes
through the earthworm gut the material is mineralized and plant nutrients are
available.

Effect of Ingestion by
Earthworms

Many studies were conducted on the process by which
earthworms transform organic matter after ingesting it and on the properties
of the resulting material, but very few were based on stabilized casts,
compared to synthetic fertilizers and compost.Orozco (1996) investigated the ability of EisinaFetida, one of the most
promising earthworms for vermicomposting, to enrich coffee pulp through
digestion.The ingested material had
no available C or N originally, but a minimum of 178 ppm
of available nitrogen and 0.86% extractable C were found in the casts, along
with higher P, Ca and Mg values, with a decrease in K content only.Earthworms increase nitrogen mineralization
rate (Pashanasi, 1992; Parmelee,
1988; Ruz-Jerez, 1992).Available N increased irrespective of the
residues the earthworms feed on or the growth temperature, which was
attributed to the increase in oxidized C due to soil ingestion, and not to
change in soil texture since the soil was not mixed(Ruz-Jerez,
1992).Binet
(1992) found the consumption of Rye grass by Earthworms to be 2.4-mg dry
weight g-1 fresh mass of earthworm day-1, and 3 times
more N was released in casts than in the soil before ingestion, which
represents 0.13 mg N / g live worm / day.Furthermore a 10% N renewal in earthworm biomass in 85 days was
observed, meaning 10% of worm-biomass N was replaced by N from the soil, and
28% of available N was due to N excretion.Extractable carbon was found to increase in soil material ingested by
earthworms, which was explained by the possible effect of indigenous enzymes
in the gut and the incomplete resorbtion of organic
C before excretion (Daniel, 1992).The
excreted polysaccharides in the earthworm gut (Arthur, 1963) could also be
responsible for this increase. According
to Lavelle (1992) high levels of ammonium are found
in fresh casts due to the excretion of NH4 through the endonephridia gland into the gut, and the mineralization
of soil organic matter by the ingested soil microflora
in the middle and posterior part of the gut.Low NO3 in fresh casts show that
nitrate isn't a metabolic product of EW (Lavelle,
1992).

(20) Since high
temperature are not part of the earthworm cast production process disease
suppressing microorganisms that may be present in this material survives in
the absence of heat.

Plant pathogens: High temperatures
are not part of organic matter processing by earthworms and casts may
inherently contain the microorganisms necessary for disease suppression. Only
a few studies have tested for suppression in earthworm casts (Szczech, et al.,
1993) and a few others for disease suppression in the presence of earthworms
- Aporrectodeaspp.
(Stephens & Davoren, 1997; Stephens et al., 1994). Szczech
& Smolinska (2001) showed a suppression of Phytophthora
sp. by earthworm casts.

Foodborne
diseases: Foodborne disease outbreaks traced to
fresh fruits and vegetables are increasingly recognized in the US.
For example, a recent literature review cites twice as many produce-related foodborne disease outbreaks between
1988-1992 as in the five year period prior to 1988 (Buck et al.,
2003).The risk of product
contamination with foodborne pathogens is a concern
for farmers using organic or conventional methods of agriculture alike.The primary source of produce contamination
in the field is believed to be either the irrigation water or a soil (amended
with manure) reservoir.Earthworms
have been exploited to accelerate biodegradation of organic wastes from
farms. Previous experiments demonstrate that Enterobacteriacea
including Salmonella are not isolated from the gastrointestinal tract of
earthworms, even when worms are raised in heavily contaminated environments (Finola et al., 1995).This data would suggest that many Gram negative bacteria, such as
those responsible for many of the foodborne
diseases, do not survive passage through the gastrointestinal tract of the
earthworm.

(21) Some composts
are suppressive of plant pathogens but heating them to60°C
for five days reduced suppressiveness. This is why
some composts need to be inoculatedwith
disease suppressing microorganisms.

Suppression of soil borne
diseases has been reported for several kinds of composts (Chung et al. 1988). Abbasi
et al. (2002) demonstrated reduced bacterial disease and anthracnose on fruit
and increased yield in organically-produced tomatoes produced in soil amended
with compost.Both compost and manure
were also shown to influence populations of plant parasitic and free-living
nematodes in transitional organic soil cropped to tomatoes (Nahar et al 2004).Populations of plant parasitic nematodes, primarily Pratylenchuscrenatus,
were inversely correlated with populations of fungal- and bacterial-feeding
and omnivorous nematodes, and with soil organic matter content.Chen et
al. (1987) showed that heating suppressive composts to 60°C for five days destroyed
suppression.Suppressiveness
was also reduced when nutrients were added to the planting mixture, which is
consistent with the hypothesis that nutrient competition between the compost microflora and the pathogen Pythiumspp.
contributes to disease suppression (Mandelbaum and Hadar, 1990).Certain types of composted pine bark suppressed Pythium damping-off diseases
when incorporated into planting mixes (Boehm et al., 1993).Since an
increase in temperature is part of the composting process, it is sometimes
necessary to inoculate composts with beneficial microorganisms (Hoitinket al.,
1993).

(22) A compost pile
needs to be 3 cubed feet to hold heat in winter and takes 3-4 months to be
cured

OSU extension:A large compost pile insulates itself and
holds the heat of microbial activity. Its center will be warmer than its
edges. Piles smaller than three feet cubed (27 cu. ft.; 3-4 ft tall) have
trouble holding this heat in the winter, while piles larger than five feet
cubed (125 cu. ft.; 5-6 ft tall) do not allow enough air to reach the
microbes at the center. These proportions are of importance if your goal is
fast, high temperature composting. Large piles are useful for composting
diseased plants or trees as the high temperatures will kill pathogens and
insects.

Moisture and Aeration

[...] The larger the pile, the
higher the temperature and the faster the composting proceeds, but only up to
a certain point. At temperatures higher than 160 degrees F, composting slows
down and charring or burning begins. This can become a problem in dry
composts, particularly in the summer.

How to Prepare and Use Compost

Remove grass and sod cover from
the area where you construct your compost pile to allow direct contact of the
materials with soil microorganisms. The following "recipe" for
constructing your compost heap is recommended for best results:

After 3-4 weeks, fork the
materials into a new pile, turning the outside of the old heap into the
center of the new pile. Add water if necessary. It is best to turn your
compost a second or third time. The compost should be ready to use within
three to four months. A heap started in late spring can be ready for use in
the autumn. Start another heap in autumn for use in the spring.

You can make compost even
faster by turning the pile more often. Check the internal temperature
regularly; when it decreases substantially (usually after about a week), turn
the pile.

(23) Organic debris are more palatable to earthworms if it’s fresh or
incubated for up to 2 weeks.The
particle size of organic matter doesn’t matter.

In Martin et al. (1992) it was shown
that when fresh material is compared to incubated material, worms prefer
fresh organic matter as in undecomposed plant
debris or debris incubated for 2 weeks.Incubation of the material fed to earthworms for 2, 5 and 10 weeks
caused an increase in growth rate and yield efficiency.With fresh plants (or plants incubated for
10 weeks or less) worms eat less and gain more weight than with material
incubated for more than 10 weeks.

Martin et al. (1992) states that
worms prefer leaves to roots: When leaves are incubated for more than 10
weeks however the material becomes only as beneficial as fresh root material:
plant material decomposed for a long time has less nutritive value.When roots are incubated for 2-5 weeks they
increase growth rate, but without a change in yield efficiency.This was explained by the fact that fresh OM has a higher water-soluble content
and more N availability.

Also in the same study all plant material have the same value after a long incubation time
since all easily assimilable compounds are
gone.When legumes and grass were
compared they gave different yield efficiency results although they both have
same N content because legumes have higher nitrogen assimilability.

As to the particle size effect, a
fraction of soil OM
was replaced with labeled C - OM. The results showed that worms ingested similar
amounts of coarse OM
(young OM – 250 – 200 µm) and fine OM (0.20µm). This indicates that
particle size does not matter (Martin et
al. ,
1992).

(24) Earthworms have
less requirements than microbes in processing carbon
and nitrogen.

Although high amounts of low
molecular weight proteins encourage microbial growth and consequently
mineralization there's a possibility that earthworms have lower requirements
than microbes in processing C and N (proteins included) since material that
goes through the earthworm gut show a higher mineralization rate than in the
case where it's just incorporated in the soil (where decomposition occurs
through microbes); Devliegher and Verstraete (1996) studied the effects of nutrient
enrichment processes (i.e. allowing the passage of organic residues from the
surface of the soil to below the surface) and those of gut associated process
(i.e. enzymatic activities in the earthworm gut that increase the nutrient
content of the ingested residues). They concluded that if the weight-increase
of the worms is accounted for, the nutrient content of ingested organic
material largely makes up for the nutrient content of the same material when
simply incorporated in the soil. Therefore we might assume that earthworm have less restrictions than microbes on protein
quality and carbon to protein ratio as related to decomposition of organic
matter.

(25) High salinity
levels and alkalinity harm earthworms. Earthworms are also sensitive to
pesticides.

A pH of 8.5
and electrical conductivity of 8 dS m-1 were found
to harm earthworms.Alklainity and salinity are harmful to both earthworms
and microorganism (Santamaria-Romero et al., 2001).Worms can be used to assess the
environmental effects of chemicals because they can predict the effect of
chemicals on other soil invertebrates. The survival rate of earthworms when a
toxic chemical is added to the soil would then be the indicator of the level
of toxicity of this chemical Edwards et al. (1992).

Edwards et al. (1992) states that
pesticides tested on worms in labs are more consistent since a standard
number of worms from the same species is in intimate
contact with the pesticides. Still soils with different absorbing capacities
have been used.He also considers that
the unvalid methods would be applying a chemical
directly to the earthworms (the results would be unrealistic), mixing a
chemical with the earthworm food (due to food repellency problems) and
injecting the tested chemical into the earthworm, since this can cause direct
injury and falsify the results.

(17) Eisenia fetida is
the most efficient in waste processing, while Eudriluseugeniae is large, fast growing, reasonably prolific
and would be ideal for protein production

Worm species

T.
tolerance

Optimum
T. and moisture

Cocoon
production

Handling
capacities

Evaluation
for waste processing

Conclusion

Eisenia fetida

0
to 35oC.

30oC

85%
moisture

number produced increases with T o . Number
hatched decreases asT o increases. Maximum reproductive rate was at 20oC.

it's
tough (can be handled, harvested)

the most efficient in waste processing.

ubiquitous

wide
To and moisture tolerance,

tough

out-competes
other species

Eudriluseugeniae

died at T o < 9oC or > 30oC.

around
25oC

reasonably
prolific

poor
handling capacities

good species to use under tropical conditions.

large fast growing reasonably prolific - would be ideal
for protein production, but has poor To tolerance and poor
handling capacities.

Perionyxexcavatus

died at T o < 9oC or > 30oC.

around
25oC

extremely
prolific

easy
to harvest

good species to use under tropical conditions.

extremely prolific easy to harvest but with
inability to handle adverse To.

Dendrobaenaveneta

less tolerant for T o
< 3oC
and 33oC.

23oC

large worm but not very prolific with a slow growth rate

large worm but not very prolific
with a slow growth rate and moderate To tolerance.

Lui, S. X., Xiong,
D. Z., Wu, D. B.1991. Studies on the
effect of earthworms on the fertility of red-arid soil. Advances in
management and conservation of soil fauna, Proceedings of the 10th
International Soil Zoology Colloquium, held at Banglador, India, August 7-13.

Zhao, S.W., Huang,
F.Z. (1988). The nitrogen uptake efficiency from 15N labeled chemical
fertilizer in the presence of earthworm manure (cast). Advances in management
and conservation of soil fauna, Proceedings of the 10th International Soil
Zoology Colloquium, held at Banglador, India, August 7-13.